I think someone would have discovered something in OPNsense by now. I'd feel a little better installing pfsense as software on my computer than buying the hardware.(Netgate) If you're talking about things like OpenWrt, I guess it would depend how much you trust the hardware vendor.I agree that CALEA is likely the main reason, but a little dark money "gift donation" having been made also isn't out of the possibility for this administration.
Honestly, I was always curious as to whether the various open source router firmwares had complied with CALEA. I haven't ever read anything anywhere saying whether any of them did or not.